Pressure switch



2 Sheets-Sheet 1 H. PURAT y PRESSURE SWITCH LAM April 21, 1942.`

Filed DeC. l2, 1940.

INVENToR Hugo Pur'dzz.

ATroRN s.

April 21, 1942. H. PURAT 2,280,262

PRESSURE SWITCH Filed Dec. l2, 1940 2 Sheets-Sheetl 2 lNvENIoR /gzYzcqa 77u ra II.; y I 4% zu@ Mmm 22W Patented Apr. 2l, -1942 PRESSURE SWITCH Hugo Purat, Detroit, Mich., assignor to Progressive Welder Company, Detroit, Mich., a corporation of Michigan y Application December 12, 1940, Serial No. 369,729

(Cl. 20G-82) 5 Claims.

This invention relates to welding apparatus and particularly relates to improved pressure switch constructions adapted for use in welding apparatus.

One of the primary objects of the present invention is to provide an improved pressure switch of the type mentioned which is eflicient and positive in its action, yet which is .economical to manufacture and simple in construction.

Another object ofthe invention is to providev an improved pressure switch of the type mentioned which may be readily adapted for use on different welding apparatus requiring different welding pressures.

Another object of the invention is to provide improved pressure responsive means for actuating an electric snap switch which is positive and sensitive in its action.

Other objects of the invention will become apparent from the following specification, the drawings relating thereto and from the claims hereinafter set forth.

In the drawings, in which like numerals are used to designate like parts throughout the se eral different views:

Fig. 1 is a side elevational view of one. type of welding apparatus having a pressure switch, according to the present invention, associated therewith;

Fig. 2 is an enlarged, vertical cross-sectional view of the pressure switch illustrated in Fig. 1;

Fig. 3 is a rear elevational view of the structure shown in Fig. 2 having a portion of the housing removed to show portions of the snap switch in elevation;

Fig. 4 is a side elevational view of the structure shown in Fig. 2 having a portion of the housing removed and showing a portion of the pressure responsive means in elevation; and

Fig. 5 is a vertical cross-sectional view, with the plunger or piston in'elevation, of a modified form of piston and sleeve assembly according to the-present invention.

In welding apparatus of the type to which'l the pressure switch of the present invention is particularly adapted, it is the practice tomove the welding electrodes into engagement with the work under pressure and to maintain the electrodes in such engagement under predetermined pressure during the welding operation, or at the time .when the welding current is being applied. According to the present invention, a pressure switch is provided which is associated with the hydraulic pressure line which forces the electrodes together so that the switch is directly re- Cil sponsive to the pressure applied to the electrodes; and the electric switch, which controls the passage of electric current to the electrodes, is not actuated until the welding pressure has been built up to a predetermined amount. Such snap switch is automatically actuated as soon as such predetermined amount is reached. As soon as the welding pressure is released or relieved, the current is automatically cut off.

Referring to Fig. 1, one form of welding apparatus is shown by Way of illustration, which is adapted to have a pressure switch according to the present invention associated therewith. The welding apparatus there illustrated is substantially that disclosed in the United States 'Patent of Wm. H. Martin, No. 2,136,490, patented August9, 1938. It is to be understood that the particular welding apparatus shown is merely to be considered as illustrative and that "the pressure switch according to the present invention is adapted for use on other types of welding apparatus as well.

The welding apparatus there shown, in general., comprises a source of-supply of an electric current I-that is transformed to produce the welding current and a source of supply of air under pressure that is conducted to a booster and transmitted hydraulically to produce the welding pressure. A source of supply of cooling liquid for cooling the electrodes and cable is also preferably provided.

The welding apparatus includes a transformer which is indicated at l0 and which may be suitably connected to the main lines of the commercial circuit. A booster l2 is connected to the transformer housing and isconnected to a suitable source of air under pressure by a conduit I4.

A welding gun is generally indicated at I6 and includes welding electrodes I8 and 20. The electrode 20 is connected to a reciprocating piston which is disposed within a cylinder 22. A conduit 24 is connected to the head end thereof for conducting the fluid under pressure to the cylinder and for forcing thev electrode 2D toward electrode I8 and thus exerting the welding pressure on the work. The piston is returned to its initial position by means of a spring 26. The conduit 2l communicates with an hydraulc source disposed within the booster I2 and has a T connection 28 interposed therein adjacent the booster housing' providing a by-pass for the fluid under pressure. A by-pass conduit 30 is associated with the by-pass of the T connection yso that it will be evident that the same pressure is exerted' in passage'30 as exists in conduit 24.

Reference may be had to the Martin patent above mentioned for a more detailed description of the apparatus so far described.

A pressure switch according to the present invention is generally indicated at 32 in Fig. 1 and is disclosed in detail in Figs. 2, 3 and 4. Referring to these figures, the pressure switch comthrough the side wall and opening through the prises a housing 34 within which a snap switch l generally' indicated at 36 is disposed. Such snap switch is of conventional construction and includes a housing 38 having the snap switch mechanism mounted therein as a unit. Such mechanism includes a pivoted switch arm 48 which is suitably fixed to the forward end of pivot shaft 42 for oscillation therewith. The pivot shaft 42 is suitably mounted on bearings fixed to a vertical partition wall 44 of the housing 38; and the rear end of the shaft 42 projects rearwardly of the housing and has a rocker member '46 fixed thereto.

The member 46 has a fiat top surface 48 and has its ends 58 and 52 tapered outwardly and downwardly slightly. A pair of stop arms 54 and 56 are pivotally mounted upon suitable pivot pins 58 adjacent the lower ends thereof; and such members 54 and 56 are each provided with inwardly disposed projections 68 adjacent the top thereof and recesses providing stop shoulders 62 against which the ends 58 and 52 are adapted to abut. The members 54 and 56 are normally urged inwardly by means of spiral springs 64.

It will thus be seen that as the rocker member 46 is rocked about its center, the shaft 42 is ro' tated or oscillated, movingor oscillating with it the contact arm 48.

The contact arm 48 has a transversely extending contact bar 66 resiliently mounted to the upper end thereof. As such arm 48 is rotated clockwise, viewing Fig. 2, the contact 66 engages a pair of separate electrical contact members 68 which are mounted within housing 38. The contact members 68 are connected to contact connections 18 and 12, respectively. Circuit lead wires, which are disposed within cable 14, are connected to the contacts 18 and 12, respectively.

Such circuit wires are connected to the circuit of the secondary, so that when the snap switch is closed, through contact of the member 66 with contacts 68, the welding current flows in the circuit of the secondary.

The cycle of operation of the welding apparatus`is provided by closing the circuit of the primary coil by means of a trigger 16, mounted on the handle of the gun, which closes a stop switch in the primary circuit.

The opposite side of the snap switch is also constructed with contacts and terminals similar to 66, 68,18 and 12, but such contacts merely serve as stops in the operation of the present structure. However, their presenceA makes it possible to connect the snap switch so that it will operate in either direction.

, The rocker member 46 is lcaused to oscillate by means of an actuating arm 18 having the lower end fixed to a shaft 88 so that such shaft is rotated or oscillatedl upon movement of the arm 18.

The shaft 88 is rotatably journaled within suitable bearings mounted on the upper-end of the housing 38 and projects rearwardly4 within the housing. A depending arm 82 is suitably fixed to the rear end of the shaft 88, so 'that itoscillates upon rotation ofthe shaft in either direction. The lower end of the member 82 is provided with an axial bore therein having oppositely disposed, longitudinal apertures 84 provided 75 lower end. vSlide members 8.6 are disposed within apertures 84 and slidably engage the side edges thereof. A roller 88 is pivotally mounted on the lower ends of members 86 by means of a pin 90; and such roller is resiliently urged into engagement with the flat surface 48 by means of a spiral spring 92 disposed within the axial bore and resiliently urging the roller 88 downwardly.

It will thus be seen that as the arm 18 is shifted, the arm 82 is correspondingly shifted so that the roller 88 rolls on the flat surface 48 and passes across the center line of the shaft 42. The arm 82 is resiliently urged toward the right, viewing Fig. 3, by meansof a spiral spring 94. As the arm 18-is moved so that the member 82 is moved clockwise, viewing Fig. 3, the lower end of member 82 rst strikes against projection 68, thereby moving it outwardly so that vprojection 58 is released from engagement with shoulder 62. `The roller 88 has then passed beyond the center of shaft 42, so that the rocker member 46 is snapped down to rotate clockwise, thereby shifting the arm 48 so that the contact 66 bridges contacts 68. The arm 56 has then been moved inwardly by spring 64, so that end 52 rests upon stop shoulder 62 of such member 56.

It will be seen that the movement of the arm 82 in this direction is resisted by the coil spring 94, and the electric contact will be maintained so long as the elements are in the position just described. If the force is released or relieved on arm 18, it will be appreciated that-the spring 94 acts to return the elements to the position shown in Fig. 3, opening the secondary circuit.

The arm 18 Ais automatically shifted in direct response to variations in the welding pressure present in conduit 24. The mechanism for automatically shifting such arm includes a walking beam member 96 which is pivotally connected substantially at its center to the upper end of actuating arm 18 by means of a pivot pin 98. The ends of member 96 are formed with forked recesses 99 which receive therein, respectively, pins I8| and |82. Such pins are xed to the upper ends of the upwardly extending arms of bellcrank members |84 and |86 which are pivotally mounted to the housing 34 by means of pivot pins |88. The other arms ||8 and ||2, respectively, of the bellcrank members |84 and |86 project outwardly for purposes that will be described in detail hereinafter.` The pins |8| and |82 provide the operative connection between bellcrank members |84 and |86 and the opposite ends of the beam member 96.

lIt will thus be seen that as the arm ||2 is moved upwardly, the beam 96 is shifted to the left, viewing Fig. 2, so that the arm 18 is rotated counterclockwise. `The means for so moving the arm 2 upwardly in direct response to pressure increase in conduits 24 and 38 comprises a piston and sleeve assembly which includes a. sleeve |I4 which is threadably received within a bore ||6 formed in the housing 34 and having the lower endthereof tapped, as indicated at ||8. The conduit 38 is connected to the sleeve `||4 by a suitable fitting so that the hydraulic pressure `within conduit 38 is transmitted directly into the interiorof bore |6.

A pistonv or plunger |28 is slidably disposed within the sleeve 4 and has a tight sliding flt with the wall thereof. The upper end of the sleeve passes through la guide ring membery |22 xedly disposed within the upper end of sleeve H4, by a split, resilient ring |23 which engages I I2 to move it upwardly.

within a groove in the sleeve. A rubber is` associated with the member |22 and the'sleeve to prevent the leakage of hydraulic nyuid through the sleeve. It will thus be seen that thepiston and sleeve assembly may be readily positioned within the housing or removed therefromjas a unit. The bore-through the sleeve and the pis-v ton |20 are oi' predetermined areas, so that such pistnn exerts a predetermined force on the per end ofthe spring I2. is received withina cupshaped member I, which Lis slidably disposed within the upper end of bore I2! and 'so positioned that the upper end of the cup |32 bears against arm 4|||| of bellcrank member |04.

The lower end oi' spring |20 is received within a o'up member lltwhich is welded to a sleeve |38 `having the exterior thereof threaded for reception within the threaded lower end of bore |2l. The member I may thus be adJustably positioned inthe bo're tc vary the resistance of spring |26. An'axially extendingguide rod |32 is-fixed to the lower end of member |34 and extends upwardly within spring |26 to prevent such spring from buckling.

Adjustable stop screws |48 are threaded through suitable tapped openings in housing 34 above the arms and ||2, respectively, to limit the upward movement oi' such arms.

It will thus be seen that as the pressure builds up in conduit 24, and, consequently, conduit I0. that the hydraulic force within such conduitstends to move the piston |20 upwardly. Such upward movement is resisted by spring |20, and

MillV associes` i than in the main embodiment above described.

vIi't'mnal changes may be made in the specific emohurlent` of the invention described without departing from the spirit and substance of the invention, the scope of which is commensurate with the appended claims.

What is claimed is:

1. A! pressure switch structure comprising a 'snap switch including a shiftable actuating arm to cause closing and opening of said switch, and pressure responsive means operatively connected to ysaid arm for shifting said arm, said means comprising a beam member pivotally connected intermediate its ends tosaid armI lever membersoperatlvely connected to the opposite ends of said beam member, a plunger disposed adjacent one endj of said beam member, means movably mounting said plunger for movement in one direction in response to predetermined pressure increase.A said plunger being so positioned that `it engages its adjacent lever when moved in said one direction to shift said' beam, and resilient means disposed adjacent the other end of said beam and engaging its adjacent lever to resist the movement of said plunger in said one direction.

the piston cannot move upwardly to shift the v is relieved, the snap switch is instantly snapped open .and the spring |28 returns the piston |20 to its initial position where it will remain until the welding pressure builds up again to its predetermined amount.

Dilferent welding pressures are proper for different apparatus or fordierent welding oper-` ations, and the construction of the present invention is adapted to be suitedto such diil'erences in the pressures desired. The apparatus may be readily adapted to a different pressure by removing the piston and sleeve assembly and inserting another in which the piston and sleeve bore are of the proper and diil'erent cross-sectional areas.

-In Fig. 5, another form of piston and sleeve assembly is illustrated in which the corresponding parts are given primed numerals. In this instance, therarea of thebore'tll' andthe crossv sectional area of the piston |20' are less than the corresponding areas of .bore I and piston |2l,.so that a greater welding pressure would be necessary to overcome the resistance of spring |26 2. A pressure switch. structure comprising a housing, a snap switch dlspOsed within said housing and including a shiftable actuating arm; a

beam member within said housing pivotally conf beam and movable in one direction in response to predetermined pressure increase, said plunger engaging the other arm of oneof said bellcrank members when moved in said one direction to shift said beam,lresilient means disposed within said housing adjacent the opposite end. of said beam, said resilient means engaging the other arm of the other of said bellcrank members to resist the movement of said plunger in said one sdirection.

3. A *pressure switch structure comprising a housing, a snap switch disposed within said housing and including a shiftable actuating arm, and pressure responsive means operatively connected to said arm for shifting said arm, said means comprising a beam member operatively connected to said actuating arm, a unitary plunger and sleeve assembly removably mounted within said housing adjacent one end of said beam member, said plunger being movable with respect to said sleeve in one direction in response to predetermined pressure increase, resilient means resisting the movement of said plunger in said one direction, and a bellcrank lever member pivotally mounted within said housing, said bellcrank member having one arm thereof operatively connected to one end of said beam member and.

having the other arm thereof positioned to be engaged by said plunger and to be moved thereby upon movement of said plunger in said one direction to thereby shift said actuating arm.

4. Apressure switch structure comprising a snap switch including a shiftable actuating arm and pressure responsive means'operatively connected to said arm for shifting said arm, said means comprising a beam member operatively connected to said actuating arm, a plunger ,movable'in one direction in response to predetermined pressure increase, resilient means resisting the movement of said plunger in said one direction, and a. belicrank lever member pivotally mounted kwithin said housing,l said rbellcrank Vmember having one arm thereof operatively connected to one end ofsaid beam memberand having the other arm thereof positioned to be engaged by said plunger and to be moved thereby upon movement of said plunger in said one div' rection to thereby shift said actuating arm.

5. A pressure switchk structure comprising a snap switch including a'Shiftable actuating arm to cause closing and opening of said switch, and

pressure responsive means operatively connected to said arm for shifting said arm, said means including a member operatively connected to said actuating arm, a plunger movable in one direction in response'to predetermined pressure 

